Cellular wireless access networks such as, for example, GSM, WCDMA and Mobile WiMAX networks, comprise a number of Base Stations, BSs, with each BS covering a geographical area, a so called cell. In each cell, there can be a number of mobile terminals or stations, MSs, and the traffic to and from the MSs in a cell is routed via the BS of that cell.
The MSs in the networks exemplified above can move between the cells, and there will be a so called “handover” made of an MS from the BS of one cell to the BS of another cell as the MS moves between those cells.
An MS which is in the so called active state can have a number of services ongoing, such as, for example, voice calls, video streaming, or best effort file download or upload. When there is a handover of an MS between BSs, the end user, i.e. the user of the MS, expects all ongoing services to be maintained, which is known as session continuity.
In order to enable handovers with a high degree of session continuity, each BS may obtain and broadcast information to its MSs about neighbouring BSs, so that an MS will be able to synchronize quickly to a new BS, and to have access to the system information of the new BS even before the handover is performed. This functionality serves to reduce the handover interruption time, and is applied, for example, in the mobile WiMAX system.
In mobile WiMAX, the BSs exchange system information with each other, in order to be able to broadcast that information to their MSs. The system information exchanged between BSs in the WiMAX system consists of a counter which is updated each time that a change is made to the system information of that BS. When an MS in the WiMAX system is handed over to a new BS, the MS will need to receive system information for the new BS, which it will receive from the new BS, which may take several seconds, during which time there may be an interruption in the services provided by the MS in question.